West Nile virus breaks out in the South

West Nile virus is on the rise in the U.S. The Centers for Disease Control and Prevention is reporting the most cases since the virus was first detected in the country in 1999.

A total of 1,118 cases and 41 deaths were reported to the CDC as of the third week in August. And 75% of the cases come from 5 states: Texas, Mississippi, Louisiana, Oklahoma and South Dakota. The numbers are trending upward.

Experts say they don't know why the outbreak is worse this year than in years past, but hot weather does seem to promote the outbreak.

"Hot weather, we know, from experiments done in the laboratory, can increase the transmissibility of the virus through mosquitoes and that could be one contributing factor," Lyle Petersen, director of the division of vector-borne infectious diseases at the CDC, said in a news briefing.

Texas has seen nearly half the cases of West Nile, a statistic that prompted the CDC to provide more than $2.5 million to support increased surveillance control including spraying. Two CDC teams went to the state to support local healthcare officials, too.

There's no vaccine for the West Nile virus, but companies are working toward solutions.

- get more from the CDC

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